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首页> 外文期刊>Journal of Materials Research >Evolution of microstructure during the thermal processing of titania and vanadium-modified titania gels
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Evolution of microstructure during the thermal processing of titania and vanadium-modified titania gels

机译：二氧化钛和钒改性二氧化钛凝胶热处理过程中微观结构的演变

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摘要

Sol-gel materials of TiO_2 and vanadium-modified TiO_2 of nominal composition 4, 8, and 16 wt.% vanadium were prepared by evaporation of aqueous colloidal sols obtained by the hydrolysis of aqueous solutions of titanium(Ⅳ) chloride with the appropriate amount of vanadyl oxalate using aqueous ammonia followed by peptization of the resulting hydrated solids using nitric acid. The nature of the sol-gel materials and their behavior on calcinations at temperatures up to 1273 K were investigated using x-ray fluorescence, powder x-ray diffraction, transmission electron microscopy, and electron diffraction and FT-Raman spectroscopy. At 333 K, all the gels comprised small (about 5 +- 1 nm) particles of anatase together with traces of brookite. The particle size changed little on thermal treatment at 573 K, but increased significantly at higher temperatures and was accompanied by transformation to rutile. Incorporation of vanadium in the gels reduced the temperature at which rutile began to appear from 923 K in pure TiO_2 to 773 K in the V/TiO_2 gels. Only rutile was present at high temperatures, except for the 16 V/TiO_2 gel, when small amounts of phase-separated vanadia were also observed. A 2-3% substitutional incorporation of V~(4+) ions in the tetragonal rutile lattice occurred at high temperatures, but the majority of the vanadium was present in an amorphous, highly dispersed fashion.
机译：TiO_2和钒改性的TiO_2的溶胶-凝胶材料，标称组成为4、8和16 wt。％的钒，是通过蒸发含水胶体溶胶而制备的，该溶胶是通过将氯化钛（Ⅳ）水溶液与适当量的氯化氢水解而获得的。用氨水制备草酸氧钒，然后用硝酸将所得的水合固体进行胶溶。使用X射线荧光，粉末X射线衍射，透射电子显微镜，电子衍射和FT拉曼光谱研究了溶胶-凝胶材料的性质及其在高达1273 K的温度下的煅烧行为。在333 K时，所有凝胶均包含锐钛矿的小颗粒（约5 +/- 1 nm）以及痕量板钛矿。在573 K热处理时，粒径变化不大，但在较高温度下粒径显着增加，并伴随转变为金红石型。凝胶中掺入钒使金红石开始出现的温度从纯TiO_2中的923 K降低到V / TiO_2凝胶中的773K。除16 V / TiO_2凝胶外，高温下仅存在金红石型，同时还观察到了少量的相分离钒。在高温下，四方金红石晶格中V〜（4+）离子有2-3％的取代掺入，但大多数钒以无定形，高度分散的方式存在。

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